Removal of pollutants from water

ABSTRACT

A method for the removal of pollutant organisms from water, which comprises contacting the water with brown coal or brown coal char.

United States Patent [191 Siviour et al.

[ REMOVAL OF POLLUTANTS FROM WATER [75] Inventors: Neil Graham Siviour,East Kew;

Grant Marshall Pearson, Elwood; Geoffrey Victor Cullen, North Balwyn,all of Australia [73] Assignee: University of Melbourne, Australia [22]Filed: July 14, 1971 [21] Appl. No.: 162,644

[30] Foreign Application Priority Data July 24, 1970 Australia 1960/70[52] US. Cl. 210/40 [51] Int. Cl B01d 15/00 [58] Field of Search 210/39,40, 3-8, 210/64, 18

[56] References Cited UNITED STATES PATENTS 1,532,775 5/1925 Sauer210/40 [451 July 1, 1975 OTHER PUBLICATIONS Babbit, H. E. Sewerage andSewage Treatment, N.Y., .1. Wiley, 1947 pp. 307-311, 316, 317, 454, 455.

Primary ExaminerChar1es N. Hart Assistant Examiner- Benoit CastelAttorney, Agent, or Firm-Bacon & Thomas [5 7] ABSTRACT A method for theremoval of pollutant organisms from water, which comprises contactingthe water with brown coal or brown coal char.

.1 Claim, No Drawings REMOVAL OF POLLUTANTS FROM WATER The inventionrelates to a method for the removal of pollutants from water. Morespecifically the invention is concerned with the use of brown coal andespecially brown coal chars as absorbents for pollutant materials,including microbial organisms and non-living pollutant substances.

It is known that certain activated carbons, usually derived frombituminous coals and activated by special processing techniques, can beused to remove organic pollutants, including microorganisms, from water.Although activated carbons are highly effective in this regard, theirhigh cost mitigates against their general use.

It has also been shown that lignite will remove up to 2 percent of theChemical Oxygen Demand (C.O.D.) from waste waters. It is the principalobject of this invention to provide a method for the removal ofpollutant organisms from water which is both effective and cheap whencompared with existing methods.

We have now found brown coal and more particularly brown coal chars willremove pollutant organisms from water with a high degree of efficiency.Furthermore, although we have confirmed that brown coal itself is notparticularly effective in the removal of other pollutant substances (asmeasured by C.O.D. we have found that brown coal chars will effectsubstantially reduction in the COD. of polluted waters, withoutresorting to any special procedures for activation of the chars.

Lignite and brown coal" are common names given to coals intermediatebetween peat and bituminous coal in both geological age and generalproperties. Brown coal and lignites have been arbitrarily defined asthose coals having a calorific value on the moist, ash free basis ofless than 10,260 Btu/1b. (See Encyclopedia of Chemical Technology, KirkOthmer (Ed.), Interscience, 1967). The American Society for TestingMaterials (see A.S.T.M. Standard D338-66 in Part 19, p. 60, Nov. 1971)classifies coal according to rank, (i.e., degree of metamorphism orprogressive alteration) and in this classification divides coals intothe four classes of Anthracitic Bituminous, Subbituminous, Lignitic. Itfurther sub-divides these classes into groups of which there are threefor anthracitic, five for bituminous, three for sub-bituminous and twofor lignitic. On the above basis, lignitic coals have a calorific valueup to 8,300 BTu/lb. The terms lignite and brown coal are not universallyused in the same sense. In the A.S.T.M. classification the entirecategory is designated as lignitic, the consolidated ones being lignitesand the unconsolidated ones being brown coal. This usage is followed insome other countries but in Germany and many other European countries,and in Australia brown coal is the generic term for the whole class,lignite signifying the firmer, fibrous, woody variety. In thisspecification, the term brown coal will be used in the last-mentionedgeneric sense, except where the context requires a narrowerinterpretation, i.e. where specific samples of coals are being referredto, and will refer to material falling within the A.S.T.M.classification of lignitic coals.

Chars may be produced from brown coals by heating at any temperaturebetween about 200 and about 1200C; even higher temperatures maysometimes be used. Brown coal from Yallourn, Victoria, Australia, whichhas been used in most of our studies, has been reported to have a netcalorific value of 2920 Btu/lb. when containing 66 percent moisture,9,000 Btu/lb. when containing 15 percent moisture. Char derived byheating this brown coal at 850C has been reported to have a netcalorific value of 13,700 Btu/lb. One method for producing char consistsin heating the brown coal from to 200C. over 8-10 hrs, then to 600 for78 hrs., and 850C for a further l-2 hrs. (See R. S. Higgins, G. L.Kennedy & D. G. Evans, The Development of Brown Coal Char as a NewMetallurgical Fuel Proc. Aus. I.M.M. Vol. September 1960.)

According to one aspect of the present invention, there is provided amethod for the removal of pollutant organisms from water, whichcomprises contacting the water with brown coal or brown coal char (bothas hereinbefore defined).

In another aspect, the invention provides a method for the removal ofpollutant organisms and/or other pollutant substances from water, whichcomprises contacting the water with a brown coal char (as hereinbeforedefined).

The solid/liquid ratio required for the method will depend generally onthe level and type of pollution initially present in the water, thedesired degree of pollution removal, and the time of contact, as well asthe actual absorbent selected, i.e. whether brown coal or char. Underideal conditions, using brown coal char at a solid/liquid ratio of 1:10and contact time of 2 hours up to 99.99 percent of coliform organismscan be re moved from polluted water. Over the same 2 hour period, browncoal char at the same solid/liquid ratio will reduce the COD. of thesame polluted water from 42 to 12 ppm. These figures, of course aremerely illustrative and are not to be taken as limiting the invention.Generally, however, solid/liquid ratios of 1:10 to 1:500 are consideredmost useful. The effectiveness of the treatment in the removal ofpollutant organisms is generally proportional to the relative amounts ofchar and water within this range of solid/liquid ratios. Removal isequally effective for contact times of 5 minutes to 2 hours.

The manner of achieving contact between the water and adsorbent does notform a part of this invention but many suitable techniques are availablefrom the arts concerned with water treatment and general materialshandling. Among the many possibilities there may be mentioned the use ofmixer-settlers; fixed, recoverable or replaceable beds such asfilter-beds or columns; and towed or moored rafts or booms containing orcomprising the absorbent, which can be situated in streams, rivers oraqueducts.

One important advantage accruing from the use of brown coal or browncoal char as pollutant absorbers is the comparatively low cost of thesematerials compared with other absorbents. In Australia conventionalactivated carbons cost about 35 to 80 cents/1b., whereas bed moist browncoal costs about 0.05 cents/1b., and the estimated costs of dried browncoal and brown coal char are about 0.2 and 2 cents/1b., respectively.

It will be appreciated also that the brown coal or char after use can bereadily disposed of by burning. Furtheremore, if desired brown coalchars used as absorbents can be regenerated for use by heating, eg by arecharring procedure which may be simply a repetition of the originalcharring process. It will be obvious that 3 4 some char could be burntto provide heat for the reafter rains, thus leading to difficulty incomparing recharring process. sults of successive experiments. For thisreason most of The basis and practice of the invention are illustratedthe subsequent water samples were taken from an open by the followingexamples. drain in the Croydon area of Victoria, in which the pol- Thefirst two examples show the results of prelimi- 5 lution level was moreconsistent, and was much higher. nary studies to determine theeffectiveness of brown coal and its char for removing a general range ofpollut- TREATMENT METHOD ant organisms from water. In the first twoexamples both brown coal and brown 1n the subsequent examples, in whichonly brown coal char were used as the adsorbent, but subsequently coalchar was used, the effects are shown of process only the char was used.In all cases the material was variables, the adsorption capacity of thechar, and crushed to l4 Tyler mesh, and in some cases the fines methodsof re-generation of the char for re-use. e removed by washing.

It should be understood that the method of counting I h experiments h dorbent were added to the organisms invol s Some inherent especially atwater in plastic containers and shaken for the specified high Countlevels at which a Count of 900,000 times, after which the adsorbent wasremoved by filtranot be distinguished with certainty from 500,000 or 1.6i d h resulting water t he with Samples f million. However, where trendsare apparent these limthe untreated water were submitted f Organismitations can be Substantially removed counting. Specific treatmentvariables are shown in the BROWN COAL results of the experiments.

In the first two examples the effect of the treatment This was Obtainedfrom Yalloum, Victoria Australia was evaluated in terms of severalmeasures of pollution, q dried at approximately 120C to about 3 percentbut in subsequent experiments the evaluation was limmolstufe Contentited to determination of presumptive coliform and con- BROWN COAL CHARfirmed faecal coliform, the latter being the Eschericha Coli (E.C0li)generally used as an indicator of sewage This was prepared from theabove described brown pollution coal by a method based on that describedby Higgins et al. (op. cit.). K. McG. Bowling in Coal Based Filter Aidsfor Industrial Application, Proc. Aust. Inst. Min. EXAMPLE 1 Met. No.233, March 1970, p.33-9, describes methods A sample of water from theYarra River, about 100 of charring various coals, including brown coal,to obyards east of Princes Bridge, Melbourne, Victoria, was tainspecific surface areas of about 700 m /g without collected during thelate summer of 1970 when it was special activation, compared with700-1500 m /g for expected that the pollution level would be high.Sepacommercial activated carbons. rate portions of the sample weretreated for 2 hours with brown coal and brown coal char, the solid toliquid WATER SAMPLES ratio (weight/weight) being 1:10. Table 1 showsthat at Initially water samples were taken from the Yarra least 99.4percent and 99.7 percent of the organisms River in Victoria, Australia,and although the degree of were removed by the coal and char,respectively, and pollution was found to be high for such a large streamTable 1A shows that the COD. of 42 ppm. was rethe pollution level wasfound to decrease considerably duced to 37 ppm. and 12 ppm.

Table 1 Results of Experiments on Adsorption of Pollutant Organisms fromYarra River Water (A) Untreated water (B) Water after Contact with driedbrown coal for 2 hours; solid/liquid ratio 1:10.

(C) Water after contact with brown coal char for 2 hours; solid/liquidratio 1:10.

'Es'c/leric/m Cali Type 1 is an organism used as a standard indicator ofsewage pollution. 'Confirmed Coliform refers to the general coliformgroup of organisms.

"The 37 plate test is Conducted after holding the plate at 37C for 24hrs. and is used as an indicator of the count of organisms originatingfrom wann blooded animals and humans.

'The 22 plate testis conducted after holding the plate at 22C for 3days. and is used as an indicator of the count of organisms originatingfrom general soils and the environment.

Table 1A Results of Experiment on Adsorption of Pollutant Organisms andOxygen Consuming Materials from Yarra River Water.

Type of pollution test (A) (B) (C) Chemical Oxygen Demand. (C.O.D.)(ppm) (A) Untreated water (13) Water after contact with dried brown coalfor 2 hrs. solid/liquid ratio 1:10 (C) Water after Contact with browncoal char for 2 hrs: solid/liquid ratio 1:10

EXAMPLE 2 This experiment was done to determine the effective ness ofthe treatment in a shorter time, i.e. 12 minutes.

At the time of this experiment heavy rains had diluted the pollution inthe Yarra River, so to obtain a pollution level comparable with theearlier experiment, raw sewage was added to the water. The results ofthe experiment are given in Table II, and it will be seen that even inthe much shorter time at least 92.9 percent of the organisms wereremoved by the brown coal, and at least 97.7 percent by the char.

Table 11 EXAMPLE 4 The results of this experiment in Table IV show thatthe removal of organisms is affected by lowering the solid to liquidratio, but even at 1:100 the removal is 82 percent for faecal Coliformin minutes contact.

""Presumptive Coliform. 1.800.000: Faecal Coliform. 1.000.000organisms/100 mls.

Results of Experiment on Adsorption of Pollutant Organisms from YarraRiver Water Containing Added Raw Sewage Effluent.

Type of Organisms Organisms Organisms Organisms Organisms pollution per100 per 100 Removed per 100 Removed count mls mls (7:) mls (7r)Eschericlia (o/i Type 1" 35.000 2.500 92.9 800 97.7 Confirmed Coliform900.000 55.000 93.9 3,500 99.6 37 plate test 3,800,000 64,000 98.333,000 99.1 22 plate tesrw 19.600.000 129.000 99.3 266.000 98.6

". & 'see footnotes in Table l. (D) Untreated water containing addedsewage effluent (E) Water after contact with dried brown coal for 12mins; solid/liquid ratio 1:10

(F) Water after Contact with brown coal char for 12 mins; solid/liquidratio 1:10

EXAMPLE 3 Table 111 Adsorption of Coliform Organisms in Croydon DrainWater by Brown Coal Char. Effect of Period of Contact.

Organisms Removed (9:)

Solid/liquid Contact Presumptive Faecal ratio time (min) ColiformColiform Original water 1:25 5 99.4 99.6 1:25 10 981 99.5 1:25 20 98.799.5 1:25 99.7 99.4

"'Presumptive Coliform. 1,80U.000; Faecal Coliform, 1,000,000organisms/I00 mls.

EXAMPLE 5 This experiment was done to determine the total capacity of agiven sample of char for adsorbing organisms. It was recognized that inpractice (in a fixed filter type bed, for example) some of the fine charwould be carried away by the water stream; so one test done on the charas-crushed and then six successive tests were done with a further samplefrom which the tines had been removed by water washing. Finally, thechar after the sixth contact was washed with unpolluted water todetermine whether the organisms were killed by contact with the char.From Table V it will be seen that the char containing the fine char isprobably more effective than the washed char, and that the ability ofthe washed char to adsorb further organisms steadily decreases with eachsuccessive contact, except between the first and second contact which isprobably indicative of experimental error in organism counting. It willalso be seen that some organisms have fact been killed and can beremoved by washing.

Table v Adsorption of Coliform Organisms from C roydon Drain Water byBrown Coal Char. Effect of Multiple contacts. (20 minute contact. Solidto liquid ratio I225) Organisms Removed (7:

Test Presumptive Faecal Coliform Coliform Original water"' Singlecontact of char* 955 98 First contact* 1 1 89 Second contact 96 Thirdcontact 89 Fourth contact 78 Fifth contact 66 Sixth contact 44 Char fromsixth contact washed Unwashed char as in Tables III & IV. "Char washedto remove fines. l6 'Presumptive Coliform, l.8tl().0(l(); FueculColiform. 1.000.000 organisms/I mls.

EXAMPLE 6 This experiment comprized two series of tests to compare theperformance of brown coal char with commercial activated carbon. Theresults show that brown coal char and activated carbon are reasonablysimilar in performance for the first contacts, but in successivecontacts the char is probably only about half as effective.

Table VI Adsorption of Coliform Grganisms'in C roydon Drain Water byBrown Coal Char and Active Carbon. Effect of Multiple Contacts. minutecontact. Solid to liquid ratio 1:20)

Organisms Removed (72 Test Faecal Coliform First Series Original Waterlst contact with char 98 3rd 39 5th 39 7th 61 lst contact with activecarbon 95 3rd 8| 72 Second Series Original water lst contact with char78 2nd 65 3rd 4th 5th 44 lst contact with active carbon 65 2nd 3rd 445th 44 -"Presumpti\'e colifonn. l 800.000; Faecal Coliform..l.000.000organisms/I00 mls EXAMPLE 7 In a series of experiments to determine thesuitability of various methods of regenerating the char for reuse, theloaded adsorbents from some of the test series described in Experiment 6were treated in various ways. From Table VII it will be seen thatburning some of the char seems to be the most effective method ofregeneration, that heating at 125C is reasonably effective and boilingin water gives negligible regeneration. It will also be seen thatalthough the performance of the regenerated char is generally comparablein the first contacts, with the original char, the performance of theregenerated char is generally not as good in subsequent contacts.

Table VII Adsorption of Coliform Organisms by Regenerated Brown CoalChar. Effect of Multiple Contacts in Water from Croydon Drain. (20minute contacts. solid to liquid ratio l:20)

*Original water. *Count higher than in original water.

We claim:

1. A method for the removal of pollutant microorganisms from water,which comprises contacting the water with a brown coal char, separatingthe char from the water after contact, wherein the brown coal char ispresent in a weight ratio of brown coal char to water of from about 1:10to 1:500 and the brown coal char is contacted with the water for atleast about 5 minutes.

1. A METHOD FOR THE REMOVAL OF POLLUTANT MICROOGANISMS FROM WATER, WHICHCOMPRISES CONTACTING THE WATER WITH A BROWN COAL CHAR, SEPARATING THECHAR FROM THE WATER AFTER CONTACT, WHEREIN THE BROWN COAL CHAR ISPRESENT IN A WEIGHT RATIO OF BROWN COAL CHAR TO WATER OF FROM ABOUT 1:10TO 1.500 AND THE BROW COAL CHAR IS CONTACTED WITH THE WATER FOR AT LEASTABOUT 5 MINUTES.